In the tests I did, the XML method was slightly faster, but required less scans and reads from disk/cache. Speed differences, in many cases, were as few as 1 or 2 milliseconds. But the reduced reads and scans means less I/O bottleneck. May not matter on some systems, but worth it in many cases.

(I ran the same tests on a While loop version, and both XML and Numbers versions were consistently at least twice as fast, many times three or more times faster, and in at least one case it was impossible to judge because XML and Numbers ran in less than a millisecond but the While loop took 37 milliseconds. The While loop, on the other hand, also requires less I/O than the Numbers table. If CPU resources are less of a bottleneck on a server than I/O, and XML isn't an option, the While loop might be viable.)